COMPUTER-SIMULATION OF VAPOR-LIQUID-EQUILIBRIA OF LINEAR QUADRUPOLAR FLUIDS - DEPARTURES FROM THE PRINCIPLE OF CORRESPONDING STATES

Vapor-liquid equilibria of different quadrupolar linear Kihara fluids have been studied, by using the Gibbs ensemble Monte Carlo technique. Coexistence curves for fluids with elongations L=L/sigma=0.3, 0.6, an d 0.8 and different quadrupoles are given. We analyze the effect of qu adrupole moment on critical properties. Quadrupole moment increases th e critical temperature, pressure, and density. The magnitude of the in crease depends on both anisotropy and quadrupole moment. A new way of reducing the quadrupole is proposed, so that the variation of critical properties due to the quadrupole follows a universal behavior. Quadru pole provokes deviations from the principle of corresponding states. A broadening of the coexistence curve is observed due to the quadrupole . The quadrupole moment increases the slope of the vapor pressure curv e vs temperature inverse. Simulation data are used to describe vapor-l iquid equilibria of carbon dioxide. Good agreement between simulation and experiment is achieved.